Hitherto, glass has been used as an adhesive or sealing material of electronic parts, or as a covering material for protecting and insulating electrodes and resistors formed in electronic parts. In particular, along with the development of electronic parts in recent years, many types of display panels have been developed, such as plasma display panel, liquid-crystal display panel, electroluminescence panel, fluorescence display panel, electrochromic display panel, light-emitting diode display panel, gas discharge type display panel, etc.
The glass used for these is required, according to its use, to have various characteristics, such as chemical durability, mechanical strength, fluidity, electric insulation property, etc. In particular, in the case of using it as a sealing material, fluidity at low temperatures is mentioned as an important factor. In case that fluidity is insufficient, there is a risk of leak out of a sealed portion. With this, it is not possible to obtain characteristics required as display panels. Therefore, in any use, there is widely used a low melting point glass containing a large amount of PbO, which has a tremendous effect of lowering melting point of glass (for example, see Patent Publication 1).
PbO, however, has a harmful effect on human body and the environment. In recent years, there is a tendency to avoid its use, and it is under consideration to make electronic materials, such as PDP, free of lead (for example, see Patent Publication 2 and Patent Publication 3).